The contribution of inorganic and organic nutrients to the growth of a North American isolate of the mixotrophic dinoflagellate, Dinophysis acuminata

Abstract

Diarrhetic Shellfish Poisoning (DSP) is a globally significant human health syndrome most commonly caused by dinoflagellates of the genus Dinophysis. While ecosystem studies suggest that blooms of this mixotrophic dinoflagellate can be promoted by excessive nitrogen (N) loading, it is unclear whether these effects are direct (nutrient stimulation of Dinophysis) or indirect (nutrient stimulation of prey) since this alga is mixotrophic and culture studies investigating the effects of nutrients on Dinophysis have not been performed. We established an isolate of Dinophysis acuminata from New York waters and conducted controlled culture experiments to assess the effects of nutrients on the growth of this dinoflagellate with and without its prey, Mesodinium rubrum. Dinophysis was found to rapidly assimilate 15 N-labeled ammonium and urea, AND to a far lesser extent nitrate. Cultures grown with and without prey generally grew faster with ammonium, glutamine, or organic matter from sewage effluent added than respective controls, while nitrate grown cultures yielded significantly more rapid growth only when fed copious amounts of Mesodinium. Growth rates of Dinophysis also increased with the amount of Mesodinium available in cultures and achieved maximal growth rates (0.36 6 0.01 d 21 ) when grown with high levels of Mesodinium and the amino acid, glutamine. Collectively, this study demonstrates that inorganic and organic N can directly promote the growth of Dinophysis and supports the hypothesis that accelerated N loading in coastal ecosystems can promote DSP producing blooms of this species and, thus, may be partly responsible for their recent expansion across the North America.

Evolutionary transition towards permanent chloroplasts? - Division of kleptochloroplasts in starved cells of two species of Dinophysis (Dinophyceae)

“…However, D . acuminata cultures could not grow for an extended period of time without prey even if supplied with ammonium or organic nitrogen forms [15]. In the present study and in the study by Hansen et al [12], lipids and starch were observed to build up in cells, indicating accumulation of organic carbon.…”

“…However, recent studies have shown that Dinophysis acuminata does not take up nitrate [14,15]. It is well-known that nitrogen availability for example determines the cellular content of light-harvesting chlorophyll protein complexes [16].…”

Toxigenic Dinoflagellates and Associated Toxins in San Jorge Gulf, Argentina

“…By contrast, the mixed southern area was characterized by the input of nutrients from deeper waters to the surface (Torres et al, 2018, in this issue). Moreover, it was recently established that ammonium uptake rates of D. acuminata were significantly higher than those of any other nitrogen source, indicating a preference for ammonium over nitrate (Hattenrath-Lehmann and Gobler, 2015), which might have allowed D. acuminata to dominate in more stratified, recycling environments toward the north and center of the SJG. This is consistent with some studies that show Dinophysis blooms can be related to cell accumulation forced by stratification (Swanson et al, 2010;Sjöqvist and Lindholm, 2011).…”

Uptake of Inorganic and Organic Nitrogen Sources by Dinophysis acuminata and D. acuta

“…Several field studies indicated a preference for regenerated forms of nitrogen in Dinophysis acuminata (ammonium and organic molecules; [15][16][17]). These trends have been confirmed in laboratory incubations of D. acuminata [18,19] which yielded no uptake, or fairly low rates, of inorganic forms of N and P, but rapid assimilation of urea. All previous results suggested that Dinophysis is either a III B1 type of mixotroph (sensu [8]), i.e., "protists that retain chloroplasts and sometimes other organelles from one algal species or very closely related algal species", or a pSNMC (plastidic Specialist Non-Constitutive Mixotroph) [7].…”